The present invention relates to a hot wire welding system which can be made very small in size.
A non-melting metal electrode and a heated filler metal are used in a hot wire welding system. Gas-shielded hot tungsten arc hot wire welding and plasma arc hot wire welding are typical examples of hot wire welding systems. A gas-shielded tungsten arc forms a weld puddle on a workpiece. A filler metal is continuously melted into this puddle behind the arc to form a weld bead. An alternating current is applied through the filler metal with the magnitude of the current adjusted so as to heat the filler metal to its melting point just as it reaches the weld. The filler metal will then form a melt line just above the surface of the puddle.
Referring to FIG. 1, a typical conventional gas-shielded tungsten arc hot wire welding system is illustrated.
In FIG. 1, reference numeral 1 designates a tungsten electrode and 3 a workpiece. A gas-shielded tungsten arc 4 is formed between the tungsten electrode 1 and a workpiece 3 by current supplied from a D.C. power source 2. A D.C. power source 6 for heating a filler metal 5 supplies the filler metal 5 with a current which flows through a contact member 7, the filler metal 5, a weld puddle 8 and the workpiece 3. The heat for maintaining the weld puddle 8 is provided by the gas-shielded tungsten arc 4. The filler metal 5 contacts the puddle 8, melts, and is deposited solely by the action of resistance heating. In this manner, welding metal 9 is formed on the workpiece 3.
Reference numeral 10 designates a nozzle for supplying the arc 4 with gas. The filler metal 5 is wound in a coil on a wire reel 11. A wire feeder 12 feeds the filler wire 5 from the wire reel 11 to the puddle 8 through the contact member 7. The D.C. power source 2 is a constant current type source, while the D.C. power source 6 is a constant voltage type source.
In this conventional gas-shielded tungsten arc hot wire welding system, two D.C. power sources 2 and 6 are required. Consequently, this system requires two transformers and two control circuits for the power sources. Hence the cost of the system is unfavorably high. Also, this system inevitably has a large physical size, and hence requires a considerably large space for installation.